# The Lathe

```Chapter
13
The Lathe
LEARNING OBJECTIVES
After studying this chapter, students will be able to:
H Describe how a lathe operates.
H Identify the various parts of a lathe.
H Safely set up and operate a lathe using various work-holding devices.
H Sharpen lathe cutting tools.
INSTRUCTIONAL MATERIALS
Part I—Parts of the Lathe
Text: pages 201–240
Test Your Knowledge Questions,
pages 239–240
Workbook: pages 69–76
Instructor’s Resource: pages 171–190
Guide for Lesson Planning
Research and Development Ideas
Reproducible Masters:
13-1 Lathe Operation
13-2 Lathe Measurement
13-3 Parts of a Lathe
13-4 High-Speed Steel Cutting Tools
(nomenclature and shapes)
13-5 Sharpening HSS Cutter Bits
13-6 Using the Cutter Bit Gage
13-7 Calculating Cutting Speeds
13-8 Cutting Speed and Feed Problems
13-9 A, Checking Center Alignment
13-9 B, Checking Center Alignment
13-10 Facing in a Chuck
13-11 Test Your Knowledge Questions
Color Transparencies (Binder/CD only)
Have students read and study pages
201–211. Review the assignment using Reproducible Masters 13-1, 13-2, and 13-3 as overhead
transparencies and/or handouts. Discuss the
following:
• How a lathe operates.
• How lathe size is determined.
• Major parts of the lathe.
• Preparing a lathe for operation.
• Cleaning a lathe.
• Lathe safety.
• Emphasize the importance of lubricating
and checking over a lathe before
operating.
GUIDE FOR LESSON PLANNING
Because this chapter is rather extensive, it
should be divided into several segments. Teach
the segments that best suit your program.
Part II—Cutting Tools and Tool Holders
A selection of cutting tools and tool holders
should be available for the class to examine.
Have students read and study pages
211–219. Review the assignment using Reproducible Masters 13-4, 13-5, and 13-6 as overhead
transparencies and/or handouts. Discuss the
following:
• High-speed steel (HSS) cutting tools and
how they are shaped for different types of
turning.
171
172
Machining Fundamentals Instructor’s Resource
• How to sharpen high-speed steel cutting
tools.
• Carbide-tipped cutting tools.
• Indexable insert cutting tools.
• How the shape of an insert determines its
strength.
• The reason for a chip breaker on a single
point tool.
• The nine basic categories of cutting tools.
• Emphasize how to handle sharpened cutting tools to prevent injury and premature
dulling.
Part III—Cutting Speeds and Feeds
Have students read and study pages 220–222.
Review the assignment using Reproducible
Master 13-7 as an overhead transparency and/or
handout. Discuss the following:
• The factors that effect cutting speeds and
feeds.
• How to calculate cutting speeds and
feeds. Use Reproducible Master 13-8 to
provide practice in calculating cutting
speeds and feeds.
• How lathe speed and carriage feed is set
on the lathes in your shop/lab.
• Reason for making roughening and finishing cuts.
• How depth of cut is determined on lathes
• Demonstrate the difference between
roughing cuts and finishing cuts. All students must wear approved eye protection
during the demonstration.
Part IV—Work-Holding Attachments
Several lathes should be set up to show
work mounted between centers, mounted in
various types of chucks and collets, and bolted
to a faceplate.
Have students read and study page 222.
Discuss and demonstrate the various work
holding attachments set up on the lathes.
Explain the safety precautions that must be
observed when mounting the attachments on
the lathe and when they are being used.
Part V—Turning Between Centers
Have a lathe set up for turning between centers plus a selection of the equipment necessary
for turning between centers.
Students should read and study pages
223–231. Review the assignment using Reproducible Masters 13-9 A and B as overhead transparencies and/or handouts. Demonstrate turning
between centers. After the demonstration, discuss
and encourage questions on the following:
• How to set up a lathe for turning between
centers.
• Proper depth to drill center holes.
• How to check for center alignment.
• Selecting the proper size lathe dog.
• Proper way to mount work between
centers. (Why a ball bearing center is preferred to a dead center.)
• Facing work mounted between centers.
• Facing to length.
• How to position the tool holder and cutting
tool.
• Rough and finish turning.
• Turning to a shoulder.
• Grooving or necking operations.
• Emphasize the safety precautions that
must be observed when turning between
centers.
Part VI—Using Lathe Chucks
Set up lathes with the various types of
chucks for demonstrations and student/trainee
examination. Have students read and study
pages 231–237.
Review the assignment using Reproducible
Master 13-10 as an overhead transparency
and/or handout. Demonstrate how the various
types of chucks are used. Discuss the following:
3-jaw universal chuck.
• How to install jaws in the universal
chuck.
4-jaw independent chuck.
• How to center work in an independent
chuck.
• Using the Jacobs chuck in the tailstock
collet chuck.
• How to mount and remove chucks safely.
• Facing stock in a chuck. (How to tell
whether the cutting tool is above or below
center.)
Chapter 13
173
The Lathe
• Plain turning and turning a shoulder.
• How to safely perform parting operations.
• Emphasize the safety precautions that
must be observed when turning work
mounted in a chuck.
Briefly review the demonstrations. Provide
students with the opportunity to ask questions.
Technical Terms
Review the terms introduced in the chapter.
New terms can be assigned as a quiz, homework, or extra credit. The following list is also
given at the beginning of the chapter.
compound rest
cross-slide
depth of cut
facing
indexable insert cutting tools
plain turning
single-point cutting tool
tailstock
tool post
Review Questions
Assign Test Your Knowledge questions. Copy
and distribute Reproducible Master 13-11 or
have students use the questions on pages
239–240 and write their answers on a separate
sheet of paper.
Workbook Assignment
Assign Chapter 13 of the Machining Fundamentals Workbook.
Research and Development
Discuss the following topics in class or have
students complete projects on their own.
1. Make large scale wooden models of the
basic cutting tool shapes. They should be
cutaway models to permit the various clearance angles to be easily observed.
2. Prepare a comparison test using carbon
steel, high-speed steel, and cemented carbide cutting tools. Make the tests on mild
steel (annealed), tool steel (heat treated), and
aluminum alloy. Employ the recommended
cutting speeds and feeds. Make a graph that
will show the times needed by the various
cutting tools to perform an identical
machining operation. Also indicate surface
finish quality.
3. Develop and produce a series of posters on
lathe safety.
4. Develop a research project to investigate the
effects of cutting fluids upon the quality of
the surface finish of turned work. Prepare a
paper on your findings.
5. Show a film or video tape on the operation
of a CNC lathe or turning center.
1. c. The work rotating against the cutting
tool, which is controllable.
2. swing, length, bed
3. c. The length of the bed minus the space
taken up by the headstock and the tailstock.
4. d. All of the above.
5. They provide precise alignment of headstock and tailstock and serve as rails to
guide the carriage.
6. tool travel, spindle revolution
7. a. Fitted to the ways and slides along them.
b. Permits transverse tool movement.
c. Permits angular tool movement.
d. Used to mount the cutting tool.
8. brush, your hands
9. b, c, d, and e.
10. high-speed steel (HSS)
11. carbide cutting
12. Cutting speed indicates the distance the
work moves past the cutting tool, expressed
in feet per minute (fpm) or meters per
minute (mpm). Measuring is done on the
circumference of the work.
13. Feed
14. A. 1600 rpm
B. 200 rpm
15. 500 rpm
16. Between centers using a faceplate and dog,
held in a chuck, held in a collet, and bolted
to the faceplate.
17. Evaluate individually.
18. Checking centers visually by bringing their
points together or by checking witness
marks at base of tailstock.
19. Evaluate individually. Refer to Section 13.9.2.
20. Evaluate individually. Refer to Figure 13-76
in the text.
174
21. 3-jaw universal, 4-jaw independent, Jacobs,
and draw-in collet. Evaluate descriptions
individually. Refer to Sections 13.10.1 through
13.10.5.
22. one-third
23. To reduce chip width and prevent it from
seizing (binding) in the groove.
24. Evaluate individually.
Pages 69–76
1. b. provides slower speeds with greater
power
2. d. All of the above.
3. c. threaded spindle nose
4. d. All of the above.
5. index plate
7. 2″ paintbrush
8. machine oil
9. b. to the left
10. d. It depends on the work being done.
11. e. None of the above.
12. Round nose tool
13. The irregular edge produced by grinding
will crumble when used.
14. Chipbreakers
15. 685 rpm
16. 320 rpm
17. 84 rpm
18. 730 rpm
19. 186 rpm
20. a. 3-jaw universal
21. c. 4-jaw independent
22. b. Jacobs
23. collet; a separate collet is required for each
different size or shape of stock
24. Using a dial indicator.
25. c. 4-jaw independent, 3-jaw universal
26. Be sure to remove the chuck key before turning on the machine.
27. c. bent-tail safety
28. b. bent-tail standard
29. a. clamp-type
30. combination drill
31. Eccentric diameters will result if the headstock center does not run true.
32. b. in either direction
33. That the cutter is slightly above center.
34. That the cutter is below center.
Machining Fundamentals Instructor’s Resource
35. parting or cutoff
36. Long work should be center drilled and supported with a tailstock center.
37. A. Motor and gear train cover
B. Carriage handwheel
C. Thread and feed selector lever
D. Quick-change gearbox
E. Selector knob
F. Lead screw direction lever
G. Motor control lever
H. Backgear handwheel
I. Backgear control knob
K. Variable speed control
L. Spindle
N. Tool post
O. Compound rest
Q. Tailstock ram
R. Ram lock
S. Tailstock
T. Tailstock lock lever
U. Handwheel
V. Cross-slide handwheel
W. Rack
Y. Bed
AA. Chip pan
BB. Storage compartment door
CC. Leveling screw
DD. Tailstock pedestal
EE. Clutch and brake handle
FF. Half-nut lever
GG. Power feed lever
HH. Carriage apron
38. d. move faster or slower if the carriage is
engaged to the lead screw
39. d. changes spindle speed
40. e. None of the above.
41. e. None of the above.
42. b. engages the half-nuts for threading
43. b. engages the clutch for automatic power
feed
44. a. moves the entire unit right and left on the
ways
45. c. automatic power cross-feed
Tool travel
Work
rotation
13-1
The Lathe
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The cutting tool is fed
into the revolving work.
Cutter bit
Lathe Operation
Chapter 13
175
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D
A—Length of bed. B—Distance between centers. C—Diameter of work that can be
turned over the ways. D—Diameter of work that can be turned over the cross-slide.
C
B
A
Lathe Measurement
13-2
176
Machining Fundamentals Instructor’s Resource
Motor and
gear train cover
Carriage
handwheel
Foot
Half-nut
lever
pedestal
Tailstock
pedestal
Power feed
lever
Carriage
apron
Storage
compartment
door
Chip
pan
dial
Leveling screw
Clutch and
brake handle
Bed
Quick-change
gearbox
selector handle
Selector knob
13-3
The Lathe
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Slide gear
handle
Back gear
pin
Back gear
handwheel
Tailstock
Variable speed
ram
control
Tailstock
Tool post
Back gear
Ram
control knob
Spindle
Tailstock
center
lock lever
Carriage
Motor control
Compound
Handwheel
lever
rest
Cross-slide
handwheel
direction lever
Rack
Parts of a Lathe
Chapter 13
177
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Facing
Left-cut tools
Roughing
Side
clearance
angle
Side rake angle
Face
End
clearance
angle
Round nose
Finishing
Standard Cutting Tools Shapes
Finishing
Right-cut tools
Roughing
Back rake angle
Body
Front cutting edge angle
Side cutting edge angle
Nose
angle
Cutter Bit Nomenclature
Nose
Cutting
edge
High-Speed Steel Cutting Tools
Facing
13-4
178
Machining Fundamentals Instructor’s Resource
B
C
Center gage
Section showing
hollow-ground
clearance angle
E
2 –3
2°–3°
Back
rake
angle
13-5
The Lathe
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A
30
30°
D
Sharpening HSS Cutter Bits
Chapter 13
179
Checking end relief
n
Iro
t
s el
Ca Ste
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Bit gage being used to check accuracy after grinding cutter tip.
Checking
side relief
Section A-A
Checking side rake
angle
Using the Cutter Bit
13-6
180
Machining Fundamentals Instructor’s Resource
Chapter 13
181
The Lathe
Calculating Cutting Speeds
•
Cutting speeds (CS) are given in feet per minute (fpm), while the work speed is given in revolutions
per minute (rpm). Thus, the peripheral speed of the work (CS) must be converted to rpm in order
to determine the lathe speed required. The following formula can be used:
rpm
=
rpm
CS
D
=
=
=
CS × 4
D
revolutions per minute
cutting speed of the particular metal being turned in feet per minute
diameter of the work in inches
Suggested Cutting Speeds
and Feeds Using High Speed Steel (HSS) Tools
Material
to be Cut
Roughing Cut
Finishing Cut
0.01″–0.020″
0.001″–0.010″
0.25 mm–0.50 mm feed 0.025 mm–0.25 mm feed
fpm
mpm
fpm
mpm
70
20
120
36
Low carbon
130
40
160
56
Med carbon
90
27
100
30
High carbon
50
15
65
20
50
15
65
20
160
56
220
67
90
27
100
30
600
183
1000
300
Cast iron
Steel
Tool steel
(annealed)
Brass–yellow
Bronze
Aluminum*
The speeds for rough turning are offered as a starting point. It should
be all the machine and work will withstand. The finishing feed depends
upon the finish quality desired.
*The speeds for turning aluminum will vary greatly according to the
alloy being machined. The softer alloys can be turned at speeds upward
of 1600 fpm (488 mpm) roughing to 3500 fpm (106 mpm) finishing. High
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13-7
182
Machining Fundamentals Instructor’s Resource
Cutting Speed and Feed Problems
Name: ______________________________________________ Date: _______________ Score: ________
•
Using the formula for cutting speeds, solve the following problems. Show your work in the
space provided. Round your answers off to the nearest 50 rpm.
1. What spindle speed is required to finish turn 2.5″ diameter brass?
2. What spindle speed is required to finish turn 4″ diameter aluminum alloy?
3. Determine the spindle speed required to finish turn 1.25″ diameter tool steel (annealed).
4. Determine the spindle speed required to rough turn 2″ diameter cast iron.
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13-8
C
13-9A
Measure resulting diameters.
The Lathe
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B
Keep same tool setting and make a cut
on both shoulders.
Machine two shoulders on a test piece.
Mikehere
here
Mike
A
Using a Section of Scrap and a Micrometer
Mike here
Mike
here
Using a Test Bar and Dial Indicator
Checking Center Alignment
Chapter 13
183
184
Machining Fundamentals Instructor’s Resource
Checking Center Alignment
Tailstock
Checking Alignment by Bringing Points Together
(View is looking down on top of centers.)
Witness marks
must be
aligned
screw
screw
Checking Alignment by Checking Witness Lines on Base of Tailstock
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13-9B
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Correct tool and tool holder
positions for facing.
Less
than 90°
30°
Direction
of feed
Facing in a Chuck
Square-shoulder nubbin
left by cutter below center
Rounded nubbin left by cutter above center
Chapter 13
The Lathe
185
13-10
186
Machining Fundamentals Instructor’s Resource
The Lathe
Name: ______________________________________________ Date: _______________ Score: ________
1. ____________________________
1. The lathe operates on the principle of:
a. The cutter revolving against the work.
b. The cutting tool, being controllable, can be moved vertically across the work.
c. The work rotating against the cutting tool, which is controllable.
d. All of the above.
e. None of the above.
2. The size of a lathe is determined by the _____ and the
2. ____________________________
_____ of the _____.
____________________________
____________________________
3. ____________________________
3. The largest piece that can be turned between centers is
equal to:
a. The length of the bed minus the space taken up by the headstock.
b. The length of the bed minus the space taken up by the tailstock.
c. The length of the bed minus the space taken up by the headstock and the tailstock.
d. All of the above.
e. None of the above.
4. ____________________________
4. Into which of the following categories do the various
parts of the lathe fall?
a. Driving the lathe.
b. Holding and rotating the work.
c. Holding, moving, and guiding the cutting tool.
d. All of the above.
e. None of the above.
5. Explain the purpose of ways on the lathe bed. ___________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
6. Power is transmitted to the carriage through the feed
mechanism to the quick change gearbox which regulates
the amount of _____ per _____.
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6. ____________________________
____________________________
13-11
(continued)
Chapter 13
187
The Lathe
Name: ______________________________________________
7. The carriage supports and controls the cutting tool. Describe each of the following parts:
____________________________________________________________________________________
____________________________________________________________________________________
b. Cross-slide: _______________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
c. Compound rest: ___________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
d. Tool post: _________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
8. Accumulated metal chips and dirt are cleaned from the
lathe with a _____, never with _____.
8. ____________________________
____________________________
9. Which of the following actions are considered dangerous
9. ____________________________
when operating a lathe?
a. Wearing eye protection.
b. Wearing loose clothing and jewelry.
c. Measuring with work rotating.
d. Operating lathe with most guards in place.
e. Using compressed air to clean machine.
10. In most lathe operations, you will be using a single-point
10. ____________________________
cutting tool made of _____.
11. Cutting speeds can be increased 300% to 400% by using
11. ____________________________
_____ tools.
12. What does cutting speed indicate? _____________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
13. _____ is used to indicate the distance that the cutter
moves longitudinally in one revolution of the work.
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13. ____________________________
13-11
(continued)
188
Machining Fundamentals Instructor’s Resource
Name: ______________________________________________
14. Calculate the cutting speeds for the following metals.
The information furnished is sufficient to do so.
14. ____________________________
CS × 4
a. Formula: rpm
D
b. CS = Cutting speed recommended for material being machined.
c. D = Diameter of work in inches.
Problem A: What is the spindle speed (rpm) required to finish-turn 2 1/2″
diameter aluminum alloy? A rate of 1000 fpm is the recommended speed
for finish-turning the material.
Problem B: What is the spindle speed (rpm) required to rough-turn 1″
diameter tool steel? The recommended rate for rough turning the
material is 50 fpm.
15. Calculating the cutting speed for metric-size material
requires a slightly different formula.
15. ____________________________
CS × 1000
a. Formula: rpm =
D×3
b. CS = Cutting speed recommended for particular material being
machined (steel, aluminum, etc.) in meters per minute (mpm).
c. D = Diameter of work in millimeters (mm).
Problem: What spindle speed is required to finish-turn 200 mm diameter
aluminum alloy? Recommended cutting speed for the material is 300 mpm.
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13-11
(continued)
Chapter 13
The Lathe
189
Name: ______________________________________________
16. Most work is machined while supported by one of four methods. List them.
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
17. Sketch a correctly drilled center hole.
18. A tapered piece will result, when the work is turned between centers, if the centers are not
aligned. Approximate alignment can be determined by two methods. What are they?
____________________________________________________________________________________
____________________________________________________________________________________
19. Describe one method for checking center alignment if close tolerance work is to be done between
centers. _____________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
20. It is often necessary to turn to a shoulder or to a point where the diameters of the work change.
One of four types of shoulders will be specified. Make a sketch of each. Make your sketches on a
separate piece of paper.
a. Square shoulder.
b. Angular shoulder.
c. Filleted shoulder.
d. Undercut shoulder.
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13-11
(continued)
190
Machining Fundamentals Instructor’s Resource
Name: ______________________________________________
21. What are the four types of lathe chucks most commonly used? Describe the characteristics of
each. _______________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
22. ____________________________
22. When using the parting tool, the spindle speed of the
machine is about _____ the speed used for conventional
turning.
23. Why is a concave rake ground on top of the cutter when used for parting operations?
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
24. There are many safety precautions that must be observed when operating a lathe. List what you
consider the five most important. ______________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
____________________________________________________________________________________
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13-11
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